In a conventional tap for hot and cold water only it is well known to provide a common discharge spout, for discharging hot and/or cold water, and the spout may have two separate passages, each dedicated to one of the hot and cold water supplies, and which have discharge outlets located adjacent to, or close to each other, and so that a single jet of hot and/or cold water can be discharged. Alternatively, the spout may have a single passage, along which hot only, or cold only water may pass, upon opening of the hot or cold valves. In addition, the tap body may incorporate a pre-mixing chamber, in which hot and cold water supplies may be mixed (upon opening of both of the hot and cold water valves), prior to the mixed supply passing along the single passage in the discharge spout to be discharged as a mixed jet of hot and cold water.
It is also known to provide a discharge spout with three separate dedicated passages, corresponding to supply of hot, cold, and further liquid (filtered water), and this has the claimed advantage that there will be no “contamination” of the filtered water passage, in that it will always only convey filtered water. However, the fabrication costs of providing three separate routes for the three different water supplies through the tap body, and the provision of three separate discharge passages within the common discharge spout, make this an expensive item which is not suitable for the mass market which requires the facility to obtain occasional supply of filtered water (in addition to more regular usage of hot and/or cold water), but not at premium cost.